Materials created by dispersing nanoparticles, in a polymer matrix strive to meet the promise of enhanced and often unique properties at a reduced cost. The availability of structure-property relationships and predictive modeling are deemed necessary to tailor materials according to our needs. However, the road from detailed information at the atomistic level to macroscopic properties has been severely segmented due to diverse experimental, theoretical, and modeling methods employed to. study polymer-particle mixtures, each with their own advantages and limitations. In this perspective, we, focus on seemingly simple polymer-nanoparticle mixture's where nanoparticles are bare or grafted with chains of the same chemical constitution as the matrix. We present, a number of studies that attempt to quantitatively identify where complete miscibility, is achieved. As we discuss, features pertaining to the nanoscale dimensions of Particles continue to challenge our fundamental, understanding on polymer-particle interactions. However, through a concerted approach of theory, experiments and simulations, recent studies significantly expand our knowledge on the morphological behavior of these systems. Most, importantly, our discussion demonstrates how new developments bridge knowledge of microscopic interactions. with thermodynamic behavior, an achievement that has far more reaching implications in the area of polymer-particle mixtures.